This invention relates to an autonomic nerve activity measuring apparatus and an autonomic nerve activity measuring method for applying electric stimulation to a living body and measuring autonomic nerve activity from a pulse wave signal reflecting the constriction of a peripheral blood vessel by an autonomic nerve (sympathetic nerve and parasympathetic nerve).
A skin blood volume, an electrocardiogram waveform, etc., is representative biological information to measure the autonomic nervous system and an attempt has been made to evaluate the state of the autonomic nervous and the balance and the functionality as to which of the sympathetic nerve and the parasympathetic nerve is dominant from the heart rate and the blood pressure and frequency analysis and chaos analysis of the digital pulse volume and further pulse wave acceleration of the digital pulse volume, etc.
For example, there are a related art of evaluating the autonomic nerve function from the a-a (systolic early positive wave) time pulse wave acceleration (refer to JP-A-2004-358022), and a related art of measuring a pulse wave for about 20 seconds and determining autonomic nerve imbalance from a distribution of peak and bottom times for each beat (refer to JP-A-2007-61572, particularly “embodiment 2”).
However, although qualitative evaluation and analysis of the autonomic nerve can be conducted, disturbance of the visual sense, the acoustic sense, the smell sense, etc., has an effect on evaluating of the autonomic nerve and it is difficult to selectively evaluate the function of the sympathetic nerve and the function of the parasympathetic nerve.
Generally, if the measuring time is short, information required for diagnosis is insufficient and an error becomes large On the other hand, considering that heart rate fluctuation has periodicity, if the measuring time is simply prolonged, the effect of the disturbance is easily received and it cannot be said that the prolonged measuring time is advantageous. That is, to conduct autonomic nerve activity measurement with no error, how long the measuring time is to be set cannot quantitatively be determined.
With the circumstances as described above as the background, an objective diagnosis of the state of the autonomic nerve is conducted by applying stimulation by an acoustic signal and an image signal and keeping track of the response time and the restoration potential of the autonomic nerve from fluctuation of vital sign (Refer to JP-A-2005-329148, particularly 0033). However, a problem remains in that the diagnosis can be applied only to a person having a normal audio visual function, and under the present circumstances, there is a demand for realizing an apparatus and a method for performing excellent autonomic nerve activity measurement.
Further, generally inspiration in respiration of a living body derives from the sympathetic nerve and expiration derives from the parasympathetic nerve. Therefore, the expiration becomes a disturbance factor of sympathetic nerve measurement from the relation between the respiration and the sympathetic nerve.